Electric heating apparatus



4 Sheets-Sheet l ENVENTOR Char/55 H. Hadghns. G I

ATTO

- C. H. HODGKINS ELECTRIC HEATING APPARATUS Filed Nov. 29, 1939 Dec. 1,1942 WITNESSES:

Dec. 1, 1942. c. H. HODGKINS 2,303,460

ELECTRIC HEATING APPARATUS Filed Nov. 29,

Ill 38 INVENTOR BY I g f ATTORNEY WITNESSES:

Patented Dec. 1, 1942 2,303,460 ELECTRIC HEATING APPARATUS I Charles H.Hodgkins, Fairficld, Conn., assignor-to Westinghouse Electric &Manufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application November 29, 1939, Serial No. 306,656

5 Claims.

My invention relates in general to electric heating apparatus, and moreparticularly to apparatus of this type having a control circuit adaptedto provide a plurality of different degrees of heat from the heatingelements employed.

This type of electric heating apparatus finds one application in heatersfor cooking purposes, such as ranges, ovens and the like, and variousembodiments of my novel apparatus will be disclosed particularly forapplications of this type, although it should be understood that myinvention is applicable to any desired application of electric heatingapparatus.

One object of my invention is to provide new and improved electricheating apparatus of the above-mentioned type.

Another object of my invention is to provide a novel arrangement ofelectrical heating apparatus wherein a single control member is adaptedto provide a pluralityof different degrees of heat fromsaid apparatus.

Another object of my invention is to provide a novel arrangement ofelectrical heating apparatus wherein a single control member is adaptedto connect the heating elements to a plurality of different voltagevalues in a plurality of different relations thereto.

A further object of my invention is to provide simplified apparatus ofthis type which is efllcient in operation.

A still further object of my invention is to provide a single controlfor heating apparatus capable of connecting the apparatus in differentcircuits to obtain different degrees of heat from the apparatus, whileconfining the arcs formed by interruption of said circuits to apredetermined arcing zone.

These and other objects of my invention will become more apparent uponconsideration of the following detailed specification of preferredembodiments of my invention, and taken in connection with the attacheddrawings, in which:

Figure l is a perspective view of a control switch for controllingelectrical heating apparatus.

Fig. 2 is a plan view of the switch shown in Fig. l with the handle andcover plate removed, and a portion of the arcing shield broken away;

Fig. 3 is a bottom plan View of the switch shown in Fig. l;

Fig. 4 is a plan view of the interior of the switch similar to Fig. 2,but with the contact operating member and its indexing means removed;

another embodiment of my invention; and

Fig. 8 is a view similar to Figs-6 and 7 but showing still anotherembodiment of my invention and,

Fig. 9 is a diagrammatic view illustrating another arrangement ofheating apparatus.

The switch per se disclosed herein is particularly claimed in mycopending application, Serial No. 306,655, filed November 29, 1939, andassigned to the Bryant Electric Company.

The switch hown in Figs. 1 to 5, generally is of the multi-position typeand two methods of making contact are employed; (1) in which movable,normally spring closed contacts are operated by cams to cause thesecontacts to engage or disengage from stationary contacts, and (2') inwhich pairs of stationary segmental contacts are bridged by a slidingshoe carried by the cam which operates the spring contacts.

The connection relation of this.. switch with respect to the circuitwhich it controls is such that the circuit is always madejor interruptedby the cam operated spring contacts engaging with or separating fromtheir cooperating stationary contacts. Therefore, arcing occurs at thesecontacts only.

The relation of the segmental contacts and the sliding shoe to the camswhich operate the spring contacts is such that there is a definitetiming in the functioning of all contacts. When switch ing from oneposition to another, the sequence is as follows: The spring contacts arefirst opened by the cam. The sliding shoe moves from one set ofsegmental contacts to another set and the spring contacts are thenclosed, thereby completing the circuit. The sliding shoe and seementalcontacts can, therefore, be considered as set-up contacts or circuitselecting contacts, and no arcing can occur at this point.

Referring to the drawings, I have illustrated a switch which is mountedin an insulating casing 2, which may be of any desired heat resistantinsulating material such, for example, as a moulded insulating materialsuch as Bakelite. The insulating casing 2 includes a bottom wall 4,opposed side walls 6, and end walls 8. The bottom Wal 4 of the casing isprovided with a central aperture I for receiving a reduced end portionI2 of the switch operating shaft. Concentric with the aperture I0 in thebottom wall of the casing, there is provided concentric annular groovesI4 and I6. In the outer groove I4 there is mounted spaced arcuatecontact segments I8, 20, and 22 maintained in spaced relation by thearcuate insulating segments 28. These segments may be maintained in thegroove I4 in any desired manner, preferably by friction. The contactsegments may be of any desired conducting material such, for example, ascopper or the like. The inner groove I6 is likewise provided with spacedarcuate contact segments 24 and 26 maintained in spaced relation by thearcuate insulating segments 28. The segments are preferably slightlyraised above the adjacent surface of the bottom wall 4 of the switchcasing as shown in Fig. 5.

The operating shaft is provided with an enlarged cylindrical portion 30adjacent the re duced portion I2, and forming a shoulder 32 which isadapted to abut against the bottom wall of the switch casing to limitmovement of the operating shaft into the switch casing. The operatingshaft is also provided with an intermediate hexagonal portion 84,forming a shoulder 86 at its juncture with the portion 30, and an outerreduced portion 38 forming a shoulder 40 at its juncture with thehexagonal portion 34. The outer end of the operating shaft is reduced asat 42 to receive an operating handle I48.

A contact operating member 44 of any desired insulating material such,for example, as a moulded insulating material such as Bakelite, isslipped over the reduced end of the operating shaft I2 until theshoulder provided in the aperture through the operating member 44,engages the shoulder 36 on the operating shaft. The enlarged portion ofthe aperture through the operating member 44 is made hexagonal in shapeto correspond with the hexagonal portion 34 of the operating shaft, tolock the operating member 44 for movement with the operating shaft. Thecontact operating member 44 is formed on its lower side with integralannular concentric projections 46 positioned to be received in spacedannular depressions 48 provided in the bottom wall 4 of theswi-teh-=casi ng. These'projections 46 are provided between the sets ofcontact segments, and between the operating shaft and the inner set ofcontact segments, respectively, to reduce the creepage distance betweenthese parts. The contact operating member 44 is provided with an opening50 which opens toward the bottom wall 4 of the switch casing, and has anenlarged openendportion 52 in which is received the contact segmentbridging contact 54, which is elongated in shape and has an outwardlyextending integral projecting portion 56, extending into the.

inner portion of the aperture 50 and telescoping into one end of a coilcompression spring 58,

which bears against the bridging contact 54 at one end thereof, andengages the closed end of the aperture 50 at its other end. The coilspring 58 acts to continuously urge the bridging contact 54 intoengagement with the contact segments.

Mounted'in the two corners of the switch casing at one end thereof, arefixed contact supports 60 and I4 carrying the contact portion 62 and I6,respectively. The contact supports may be made of any suitableconducting material such as brass, copper, or the like, but thecontacting portions thereof are preferably made of a metal capable ofwithstanding repeated arcing, such as silver or a silver alloy.Cooperating with the contacting portions 62 and 16 are the resilientcontact carrying arms 64 and 18, respectively, secured in the oppositecorners of the switch casing, on conducting supporting members 66 and60, respectively. The resilient contact carrying arms carry at theirfree ends contacting portions 10 and 64 for cooperation with the contactportions 62 and I6, respectively, and are formed of a like material. Theresilient contact carrying arms 64 and 16 are stressed so as to normallyengage their contacting portions with the fixed contacts 62 and T5. Eachof the resilient contact carrying arms 64 and 18 is provided atsubstantially its mid-portion with'a struck-out part I2 and 86,respectively.

As viewed in Figs. 2 and 4, the struck-out portion 86 of the resilientcontact carrying arm 16 is struck out of the upper edge of this contactcarrying arm, whereas, the struck-out portion 12 of the other arm 64 isstruck out adjacent the lower edge of that contact carrying arm, all fora purpose hereinafter to be described. The contact carrying arms 64 andI8 are secured to the supports 66 and 80, respectively, by any suitablemeans such, for example, as by rivets 68 and 82, respectively. Alsosecured-to the support 66 by the rivets 68 is a .-fixed contact strip00, having an angularly extending contact portion 90. A substantially U-shaped resilient conducting member 92 integral with a supporting member94 secured in the switch casing in any desired manner, has one leg 96thereof extended for cooperation with the fixed contact 90. Anintermediate portion of the leg 96 is struck out as at 98 for a purposeto be hereinafter described.

The contact operating member 44 is provided with peripheral camsurfaces, as shown especially in Fig. 2. These cam surfaces are providedfor cooperation with the struck-out portions 12, 86 and 98 of the threeresilient contact bearing arms. As shown in Fig. 2, the periphery of theContact operating member is provided with outer indented portions I00,IN and I02 for cooperation only with the outer struck-out portion 06 ofthe resilient contact carrying arm "I0. These indented portions I00, MIand I02 are provided only in the outer portion of the peripheral surfaceof the contact operating member 44 as is apparent from Fig. 2. Thecontact operating member 44 is also provided with indentations I04 andI06 which extend throughout the width of the periphery of the contactoperating member 44, so as to operate, or engage with both of theindented portions 86 and 12 of the resilient contact carrying arms. Thecontact operating member 44 is further provided with an outwardly offsetprotuberance I00 for engagement only with the resilient contact arm 96.

As shown in Figs. 2 and 4, I have provided an insulating barrier I64integral with the switch casing and positioned between the fixedcontacts 62 and 16. The insulating barrier I64 is provided with arcuateextensions I66 to substantially isolate the contacts 62 and I6 from thecontact segments. A cover I is suitably secured to the open side of theswitch casing, for example, as by the machine screws I5I. Securedbetween the cover and the casing is an arcing shield I52 of insulatingmaterial such, for example, as fiber or the like, which, together withthe switch casing and the insulating barrier I64, I66, completes the..siibstantial enclosureor segregation of the contests 62 and I6 fromeach other and from the contact operating member, and contact segmentsprovided in the bottom of the switch casing.

For indexing the contact operating member in the desired operatingpositions, I have provided resilient rod elements I54 and I56, onopposite sides of the hexagonal portion 34 of the operating shaft withcorresponding ends of the resilient rods received in notches I58provided in one side wall of the switch casing, and with the oppositeends of the resilient rods received in notches I60 provided in theopposite side wall of the insulating casing, which latter notches areelongated to receive the coil compression spring I62 engaging betweenthe resilient rods I54 and I56, respectively, and the outer ends of thenotches I60.- The springs I62 act to maintain the resilient rods I54 andI56 in engagement with the opposed flat sides of the hexagonal portion34 of the switch operating shaft. Thus, in turning the shaft, it isnecessary to slightly separate the resilient rods I54 and I56 by a camaction of the hexagonal portion 34 of the switch operating shaft, untilanother set of opposite fiat surfaces on the shaft are brought intoflush engagement with the resilient rods.

' This will clearly indicate to the manipulator when an operatingposition of the switch has been reached, and the resilient rods I54 andI56 under the influence of the springs I62 will tend to maintain theswitch in its operative positions. A handle I48 is frictionally fit onthe outer end of the switch operating shaft and is provided withsuitable indicia, which will be hereinafter referred to.

The various switch connections which I have provided in this embodimentof my invention will have use primarily in the circuit shown in Fig. 6.s

The switch proper is provided with a terminal I I which has portionsextending through the casing spection of Figs. 5 and 6. All the switchterminals are provided with screws I28 for attach ing lead wiresthereto.

Referring now particularly to Fig. 6 I have illustrated in schematicform, one embodiment of volts between the positive and negativeconductors of the supply circuit and one-half that value, or 125 voltsbetween either the positive or negative conductors and the groundedneutral conbottom wall and connected with the contact segment I8 and theconducting support 66, respec- '-tively, which in turn connects thisterminal with the resilient contact arm 64 and its contact portion I0and with the fixed contact 88 and its contacting portion 90. Theterminal I I2 of the switch is electrically connected through the bottomwall of the switch casing with the support 80, thus connecting thisterminal with the resilient contact arm 18 and its contacting portion64. A terminal H4 is provided on the back of the switch and, as shown inFig. 5, includes an inner angular portion II 6 extending through thebottom wall of the casing and connected with one leg of the U- shapedresilient contact 92 shown in the upper end of the switch casing in Fig.4. The terminal I I8, also provided on the back of the switch casing onone side thereof, is provided with an integral extension I20, extendingthrough the bottom wall of the switch casing, as shown in Fig. 5, whichis in turn, integral with the contact segment 24. The switch terminal I22 at the back of the switch casing is connected through the bottom wallof the casing to the fixed contact support l4, and has an extension I23for connection with a portion extending through the bottom wall of theswitch casing for connection with the contact segment 22. The switchterminal I26 also mounted on the back of the switch casing is connectedto the fixed contact support 60 through the bottom wall of the casing,and is provided with an extension I21 for connection through the bottomwall of the casing with the contact segment 26. The terminal E24 of theswitch casing is provided with a connection through the bottom wall ofthe casing to the contact segment 20. These connections of the switchterminals with the corresponding contacts or contact segments arereadily apparent from an inductor. H2 is connected by a conductor I30 tothe posi tive conductor of the supply circuit. A conductor I32 connectsthe neutral conductor of the supply circuit with the switch terminalI24, and a conductor I34 connects the switch terminal IIO with thenegative conductor of the supply source. The terminal II4 of the switchis connected to the neutral conductor of the supply circuit through apilot lamp I 36. One end of the resistance heater element I38 isconnected by conductor I42 to the switch terminal I22. One end of theresistance heater element I is connected by the conductor I46 to theswitch terminal H8, and a conductor I44 connects the switch terminal I26to the other ends of the resistance heater elements I38 and I40.

I have illustrated in Fig. 6 the six positions of the switch used withthis particular circuit. This is capable of providing five differentdegrees of heat from the heating elements I30 and I40. At the extremeright in Fig. 6, I have illustrated the off position of the switchwherein all contacts are open and the circuit through the pilot lamp I36is broken. To the left of this, I have illustrated the first or lowestheat position, labeled the simmer position, wherein the circuit throughthe switch extends from the positive conductor of the supply sourcethrough conducill) tor I30, terminal II2, resilient contact arm 18,fixed contact '14, terminal I22, conductor I42, resistance elements I38and I 40, conductor I46, switch terminal II8 contact segment 24, bridging contact 54, contact segment 20, switch terminal I24, and conductorI32 to the neutral conductor of the supply circuit. This provides voltsacross the two resistance elements I38 and 440 connected in series, thusproviding, for example, with a resistance of approximately 62.5 ohms,and assuming unity power factor, substantially 125 watts of heatingeffort. The other four heating positions of my switch are illustrated tothe left of the "simmer position with progres sively higher heatingeffects provided by successive positions of the switch. Thus, in'theposition marked low, the heating element I36 alone is subjected to 125volts, and at the low medium" position the heating elements in seriesare connected. across 250 volts. In the medium" position, the heatingelement I38 alone is connected across 250 volts, and in high position,each of the heating elements I38 and I40 is individually connected, orconnected in parallel across 250 volts. each of the positions shown inFig. 6.

The sequence of operation of the contacts of the switch are as follows.1 The switch, as shown Figs. 1 to 5 is in the of! position,corresponding to the off position shown in Fig. 6. It will be noted thatin this position; referring As shown in Fig. 6, the switch terminal Ehevoltage and wattage are marked (or.

particularly to Figs. 2, 4 and 6, the resilient contact arms 84 and I8are maintained by the contacu operating member 44 out of engagement withtheir cooperating fixed contacts 52 and "I6, respectively. Also, theswitch operating member 44 is in a position such that the segmentbrid'ging member 54 engages only the segment 24. Also, the projectionI08 on the contact operating member is in engagement with the struck-outportion 98 on the leg 96 of the U-shaped resilient contact controllingthe pilot lamp I36, to maintain the resilient contact out of engagementwith its cooperating fixed contact 90. Upon move ment of the switchinghandle from the off position in a counterclockwise direction, as viewedin Figs. 1, 2 and 4, to the next or simmer position, it is obvious thatthe resilient cont-act bearing arms 64 and I8 will remain open until thebridging contact 54 is in a position to bridge the contacts 24 and 20,after which the struck-out portion 86 of the resilient contact carryingarm I8 registers with the indentation l04 provided on the switchoperating member 44, to permit the contacts 84 and IE to close tocomplete the circuit to the heating element I38. It is thus apparentthat the circuit is first set up by the bridging contact 54 and thecontact segments, and then the circuit is closed by the arcing contactsI6 and 84.

In moving the switch operating member from the simmer position to thenext or low position, it is obvious that the first thing that takesplace is engagement of the struck-out portion 86 of the resilientcontact carrying arm I8 with the protuberance below I08 on the contactoperating member 44 to open the contacts 16 and 84 prior todisengagement of the bridging contact 54 with the contact segments 20and 24. The bridging contact 54 then moves from engagement with thecontact segments 20 and 24 into engagement with the contact segments 20and 26, and thereafter, the indentation I06 on the contact operatingmember 44 registers with the struck-out portion 86 on the resilientcontact carrying arm 18, to permit the contacts I6 and 84 to close.

This same sequence of operations of the switch contacts takes place uponmovement of the switch to all of its six positions. In other words, thearcing contacts 16 and 84, and 62 and ID are first opened upon movementof the switch from one position to another before the bridging contact54 leaves one set of contact segments to engage with another set ofcontact segments. These arcing contacts remain open until the bridgingcontact 54 has engaged with the next set of contact segments, whereuponone or both of the arcing contacts may be closed depending upon whetherthe resistance elements are to be connected between one of the liveconductors of the supply circuit and the neutral conductor, or whetherthey are to be connected between the two live conductors of the supplycircuit. It is thus obvious that no arcing can occur at the smallcontact segments where the circuits through the switch are selected, andthat all arcing is done at one or both of the heavy arcing contacts I6,84 and 62, I0, in especially provided arcing chambers which aresubstantially insulated from the contact segments and the contactoperating member 44.

This type of switching arrangement makes it possible to reduce thenumber of contacts requiring special arcing metals, and also permits theprovision of special arcing chambers to prevent distress due tofiash-over from one arcing contact to another. The small space requiredby the segmental contacts, and sliding bridging contact, lends itselfreadily to a device of small dimension and permits great flexibilitsince a variety of arrangements of segmental contacts may be employedfor the control of difierent circuits.

In Fig. 7 I have shown another schematic form illustrating anarrangement of a switch similar to that shown in Figs. 1 to 6 forcontrolling a pair of heating elements I55 and IBI of unequalresistance, and having six positions as in Fig. 6 which includes an "ofiposition and five heating positions. The switch used in this embodimentof my invention is the same as that shown in detail in Figs. 1 to 5 withthe exception of a slightly difierent arrangement of contact segments,and hence like reference numerals are used to designate like parts.

As shown in Fig. "I the heating elements or resistors I59 and NH aresupplied from a three wire source of electrical energy similar to thatdescribed in Fig. 6.

Referring in particular to the off position shown in Fig. 7, Ihave showna conductor I 48 connecting the positive wire of the supply circuit withthe switch terminal I53, which in turn is connected with the resilientcontact arm I8 of the switch. A conductor I63 also connects the positiveconductor of the supply circuit with a terminal I61 of the switch whichis connected with the resilient contact arm 96, cooperable with thefixed contact 90, which in turn is connected with the switch terminalI66 for controlling a pilot lamp I36 in series with the conductor I60connecting the switch terminal I66 with the neutral conductor of thesupply circuit. A conductor I10 connects the neutral conductor of thesupply circuit with the switch terminal I12, which is connected with theresilient contact arm 64 of the switch. The contact segment I iselectrically connected by the conductor I65 with the contact arm 64. Theresistor I59 which has a greater resistance than the resistor I 6|, haone end thereof connected by the conductor II4 to the switch terminalI16, which is connected with the inner annular switch contact segmentI18. The resistor I6I has one end thereof connected by a conductor I80with a switch terminal I82, which is connected to the fixed switchcontact 80. The other ends of the resistors are connected by a commonconductor I51 to the switch terminal I 55, which in turn is connectedwith the fixed switch contact "I4. The negative conductor of the supplycircuit is connected as by the ,conduc tor I84 with the switch terminal[86, which is in turn connected with the switch contact segment Assumingthat the supply circuit is capable of supplying the same voltages as inFig. 6, that is, for example, 250 volts between the positive andnegative conductors and volts between the neutral conductor and eitherof the other two conductors, and further assuming by way of illustrationthat the resistor I59 consumes 1400 watts when connected across 250volts and the resistor I6 I consumes 600 watts when connected across 125volts, the several positions illustrated in Fig. '7 will give theseveral wattages marked thereon. The switch used in Fig. 7, of course,has a single controller like the switch shown in Figs. 1 to 6 and thepositions marked on Fig. 7 will correspond to those provided on thecontroller in the In the next position to the left of the on? positionor the position marked super, the connections are as follows: Onecircuit extends from the negative conductor of the supply circuitthrough conductor I84, switch terminal I86, contact segment I88,bridging contact 54, contact segment I18, switch terminal I16, conductorI14, to one end of the resistor I59, to the conductor I51, switchterminal I55, switch contact 14, resi1 ient contact arm I8, switchterminal I53, conductor I49 to the positive conductor of the supplycircuit, thus providing for the voltage values given above, 250 voltssupplied to the resistor I59. The circuit for the other resistor I6Iextends from the conductor I51 and the positive conductor of the supplycircuit in the manner stated above through the resistor I6I, conductorI80, switch terminal I82, switch contact 60, resilient switch contactarm 64, switch terminal I12, conductor I10 to the neutral conductor ofthe supply circuit, thus providing 125 volts supply for the resistorIBI, thus with the values given above, providing a total of 2,000 wattsfor the two resistors in the position marked super of Fig. 7.

In th next position marked simmer the two resistors are connected inseries across a pair of supply conductors supplyin 125 volts. In thenext position marked high the resistor I59 alone is connected across 250volts; in the next or medium position the resistor IBI is connectedacross 125 volts, and in the final or low position the resistor I59alone is supplied with 125 volts. It is also to be noted that in eachposition excepting the off position the circuit through the pilot lampI36 is closed bythe movable contact 96.

It should be noted in connection with this embodiment of my inventionthat I have provided one position, th simmer position which is thelowest heat position, in between the two highest heat positions. This isadvantageous when it is desired to heat a relatively large mass quicklyup to a certain temperature by use of either of the two higher heatpositions, and then maintain it at that temperature by supplying arelatively small quantity of heat thereto for a relatively long periodof time, which can be readily accomplished by merely turning the controlto the adjacent simmer position, conveniently located intermediate thehigher and super positions of the switch.

The operation of the switch in this embodiment of my invention is thesame as that described in the previous embodiment. In other words, thearrangement is such that the circuit is always opened or made at thecontact 60 and/or I4, before the bridging contact moves from engagementwith one set of segmental contacts into engagement with another set.Thus, the circuit is first set up by the bridging contact 54 engagingwith the contact segments and then the segment is closed by the arcingcontacts I4 and 60. Due to the different arrangement of contact segmentsin this embodiment of my invention, the contact operating member of thisswitch will necessarily be formed with a different cam portion foroperating the resilient contact arms 64 and 18 than that provided forthe switch shown in Figs. 1 to 5.

As in the previous embodiment of my invention this same sequence ofoperations of the switch contacts takes place upon movement of theswitch to all or its six positions. In other words the arcing contacts60 and 14 are first opened upon movement or the switch from one positionto another before the bridging contact 54 leaves one set of contactsegments to engage with another set. These arcing contacts remain openuntil the bridging contact 54 is in engagement with the next set ofcontact segments whereupon one or both of the arcing contacts may beclosed depending upon which of the supply conductors are to be connectedto the resistors.

In the embodiment or my invention shown in Fig. 8, I have shown afour-position switch caductor I92 connects the positive conductor of thesupply circuit with a switch terminal I94, which is connected with theresilient switch contact I9. A conductor 202 also connects the positiveconductor of the supply circuit with the switch contact 204 cooperablewith the resilient switch contact 96 connected by a conductor 206 withthe neutral conductor of the supply circuit. Included in the conductor206 is a pilot lamp I36. A conductor 208 connects the negative conductorof the supply circuit with the switch terminal 2I0 which is connectedwith the resilient switch contact 64. The neutral conductor of thesupply circuit is also connected by a conductor I96 with the switchterminal I98 electrically connected with the inner contact segment 200.The resistors 2 I4 and 2 I6 are connected by a common conductor 2I2 to aswitch terminal 2I3, which in turn is connected with the contact segment2I8. The other end of the resistor 2 is connected by a conductor 220with the switch terminal 222 which in turn is connected to the fixedswitch contact I4, electrically connected with the contact segment 224.The other end of resistor 2 I 6 is connected by a conductor 2 I 1 withthe fixed switch contact 60. The resistors 2 and M6 in this embodimentof my invention are designed to give their greatest heating effect whencon nected across a voltage corresponding to that obtained betweeneither the positive or negative conductors of the supply circuit, andthe neutral conductor.

Thus in the first or high" position shown in Fig. 8, the resistors areconnected as follows: from the positive conductor of the supply circuitthrough conductor I92, switch terminal I94,

switch resilient contact arm I8, contact 14, switch conductor 208. Thus,for the same voltage values' given in connection with the two previouslydescribed embodiments in this position the resistors 2M and 2I6 will beconnected in parallel across volts.

In the intermediate or medium position shown in Fig. 8, the resistor 2|Balone is con nected across a pair of supply conductors supplying 125volts. In the low position shown in Fig. 8, the connections establishedby the switch are such as to connect the two resistors in series with apair of supply conductors furnishing 125 volts. The switch used in Fig.8 has a sequential operation of its several contacts the same as theswitch described in connection with the other two embodiments of myinvention. In other words, the switch contacts ar preferably operated ina manner so that the circuit is always made or broken at the arcingcontacts 60 and/or 14, so that the bridging contact 54 is moved from oneset of segments to another only when the circuit has previously beenopened at the arcing contacts.

In the embodiment of my invention shown in Fig. 9, I have illustrated aneight position switch capable of providing six different degrees of heatwith two off positions. The heating arrangement shown in Fig. 9 utilizesa heating element comprising two resistance elements 228 and 230 ofunequal value. The switch employed in this embodiment of my invention isalsoof the same general type heretofore described, differing only fromthe switch shown in Figs. 1 to in the number of positions to which theswitch may be moved and, of course, in the particular arrangement andnumber of contact segments to obtain the desired circuit connections.Accordingly, like reference numerals will be used to designate likeparts.

In order to avoid complicating the drawings, it

i will be noted that I have applied reference characters in Fig. 9 as inFigs. 6 to 8, inclusive, only to those circuit connections and partswhich are connected to supply conductors in the particular positioninvolved. Thus, no numerals have been applied to the parts andconnections in the two off positions. Considering the lowermost or superposition shown in Fig. 9, the circuit proceeds from thenegativeconductor of the supply circuit through the conductor 236 to theswitch terminal 234, resilient contact arm 64, fixed contact 60, andconductor 232 to one end of the resistance heating element 228. Theheating elements 228 and 230 are joined at one end by a common terminal,which is connected by a conductor 226 to switch contact I4, resilientcontact arm I8, switch terminal 225, and conductor 223 to the positiveconductor of the supply circuit. The other end of resistance element 230is connected by a conductor 238 with the switch contact segment 240, byway of bridging contact 54, contact segment 242 and conductor 244 to theswitch terminal 234, and conductor 226 to the negative conductor of thesupply circuit. Thus, it can be seen that in this position of the switchboth heating elements 230 and 228 are connected in parallel across thepositive and negative conductors of this supply circuit, thus supplying,for example, 250 volts to each heating element.

Without going into detail as to the circuit connections in the next orhigh position, it is apparent from the conductors numbered that theheating element 230 alone, is connected across the positive and negativeconductors of the supply circuit. Similarly, in the next or intermediateposition, the resistance element 228 alone is connected across thepositive and negative conductors of the supply circuit. The nextposition is an 011' position of the switch which is located intermediatethe six heating positions of the switch to thereby avoid the necessity01' turning the switch a relatively great distance when it is desired toturn the switch oif" from any one of the heating positions thereof. Inthe medium position, the resistance element 230 alone is connectedacross the positive conductor of the supply circuit and the neutralconductor to thereby obtain a reduced voltage on this resistanceelement, as compared to the position in which this resistance isconnected across the positive and negative conductors of the supplycircuit. In the next position or low position seen in Fig. 9, theresistance element 228 alone is connected across the neutral andnegative conductors of the supply circuit. In the simmer" position, thetwo resistance elements 228 and 230 are connected in series across theneutral and negative conductors of the supply circuit. Inasmuch as thiscircuit involves conductors not heretofore described, it will be tracedin detail. As seen in the second position from the top in Fig. 9 of thedrawings, the upper end of resistor 23! is connected by the conductor238, contact segment 240, bridging contact 54, contact segment 246, andconductor 24! to the neutral conductor of the supply circuit. The lowerend oi resistance 228 is connected by a conductor 232 to the fixedswitch contact 60, resilient contact arm 64, switch terminal 234 andconductor 23! to the negative conductor of the supply circuit. As shown,the common terminal of the resistors 22! and 230 is not connected to anysupply conductor in this position.

Thus, progressing in a downwardly direction, the respective positionsshown in Fig. 9 denote respective circuit arrangements in which theresistor elements 228 and 230 are so connected to the supply conductorsas to give progressively greater heating effects, assuming, of course,that the resistor element 230 is of greater value than the resistorelement 228. It will also be noted that the first three heatingpositions 0! the switch involve connections of the resistor elementseither in series or singly between one of the live conductors of thesupply circuit and the neutral conductor which, following the previousexample, may supply a voltage of 125 volts. Following these threepositions is an 011" position, after which the resistors are connectedto the two live conductors of the supply circuit, both singly andfinally in parallel relation. The voltage obtained between the supplyconductors in this embodiment of my invention may be as describedheretofore, by way oi example, 250 volts between the positive andnegative conductors and one-half that value or 125 volts between eitherthe positive or negative conductors and the neutral conductors.

As stated above the switch in the circuit arrangement shown in Fig. 9operates with a sequential operation of its several contacts in the Isame manner as the switch described in connection with Figs. 1 to 5. Inother words, the switch contacts are operated in a manner so that thecircuit is always made or broken at the arcing contacts 60 and/or 14, sothat the bridging contact 54 is moved from one set of contact segmentsto another only when the circuit has previously been opened at thearcing contacts.

From the foregoing it should be obvious that the general type of switchdescribed in connection with Figs. 1 to 5 of the drawings is capable ofuse in a plurality of diflerent novel circuit arrangements for theconnection of plural elewire supply circuit be provided providingdifierent voltages between different pairs of conductors, and inconnection with the embodiments of Figs. 7 and 9, that a heating elementbe provided embodying unbalanced sections. The specific voltage,resistance or wattages are immaterial, since obviously the circuits Ihave shown can be used in connection with any desired voltage or anydesired plural resistor heater assembly.

Having described preferred embodiments of my invention in accordancewith the patent statutes, I wish it to be understood that my inventionis not to be limited, to the particular embodiments disclosed hereinsince it will be obvious, particularly to persons skilled in the art,that many changes and modifications may be made in these particularstructures without departing from the broad spirit and scope of myinvention. Therefore, I desire that my invention be interpreted asbroadly as possible and that it be limited only by what is set forth inthe appended claims.

I claim as my invention:

1. In an electrical system for connection with a three wire supplycircuit, a plurality of load devices, movable selector contact means forsuccessively energizing a plurality of spaced selector contacts uponmovement of an operating means for said selector contact means in onedirection, electrical connections arranged to connect one or more ofsaid load devices in a plurality of different relations with respect tosaid supply circult when difierent ones of said selector contacts areenergized at difierent positions of said movable operating means andincluding a plurality of arcing switches each having a pair of separablecontacts in certain of said connections, with certain of said selectorcontacts connected, respectively, to one of said supply wires and to oneterminal of said load devices, and with one contact of one of saidarcing switches connected to another of said supply wires and anotherselector contact, and the other contact thereof connected to a terminalof said load devices, the other arcing switch having one contact thereofconnected to the third supply wire and its other contact connected to athird terminal of said load devices, and common operating means for saidmovable selector contact means and said arcing switches for energizingsaid spaced contacts in succession and for opening the contacts of atleast one of said arcing switches prior to deenergizing a spacedcontact, and for closing the contacts of at least one of said arcingswitches only after energizing the next succeeding spaced contact, andoperative to close said one arcing switch at least at one operativeposition of said switch operating means and to open said one arcingswitch at least at one other operative position of said switch operatingmeans.

2. In electric heating apparatus having a plurality of supply conductorsadapted to be connected to a plurality of conductors leading from asource of electrical energy so that difierent pairs of said supplyconductors are provided with resistors: the combination of selectorswitch means having movable contact means adapted to successivelyenergize a plurality of spaced contacts', means including electricalconnections constructed and arranged to establish different circuitsbetween one or more of said pairs of conductors and one or more of saidresistors when said spaced contacts are energized, respectively, arcingswitch means in each of said different circuits, said connectionsincluding direct connections from a pair of said supply conductors tosaid selector switch means and at least one direct connection betweensaid selector switch means and at least one terminal of said resistors,

'one of said arcing switch means connected bev tween one of said lastmentioned pair of supply conductors and another terminal of saidresistors, another arcing switch means connected between the thirdsupply conductor and a third terminal of said resistors and saidselector switch means, and common operating means for moving saidmovable selector contact means to deenergize one of said spaced contactsto energize another and for opening the contacts of at least one of saidarcing switches prior to movement of said movable selector contact meansto deenergize said one spaced contact, and for closing the contacts orat least one of said arcing switches only after movement of said movableselector contact means to energize said other spaced contact.

3. In electrical apparatus for connection with a three-wire supplycircuit, a plurality of load devices, selector switch means includingmovable contact means for successively energizing a plurality of spacedcontacts upon movement of operating means therefor in one direction,electrical connections arranged to connect one or more of said loaddevices in a plurality of different relations with respect to saidsupply circuit corresponding to different positions of said operatingmeans including a pair of arcing switches each having a pair ofseparable contacts in certain of said connections, with certain ofdiflerent electromotive forces and a plurality of 7 said selectorcontacts connected, respectively, to

one of said supply wires and to one terminal of said load devices, andwith one contact of one of said arcing switches connected to another ofsaid supply wires and another selector contact, and the other contactthereof connected to a terminal of said load devices and to stillanother another of said spaced contacts, and common operating means forsaid movable selectorcontact means and arcing switches for opening thecontacts of at least one of said arcing switches prior to deenergizationof a spaced contact, and

for closing the contacts ofat least one of said arcing switches onlyafter energization of the next succeeding spaced contact.

4. In electric heating apparatus, a three wire supply circuit having aneutral conductor, a pair of resistors having a common terminal,selector switch means having movable contact means adapted to beconnected to said neutral supply conductor and adapted to successivelyengage at least two spaced contacts upon movement oi operating meanstherefor in one direction, said spaced contacts connected to said commonre-' sistor terminal and one other resistor terminal, respectively, apair of arcing switches each having a pair of separable contacts, one ofsaid areing switches connected between another supply conductor and saidone other resistor terminal, the other of said arcing switches beingconnected between the third supply conductor and third resistorterminal, common operating means for said switches operative in threesuccessive positions thereof to maintain said other arcing switch closedin each position, to close said one arcing switch only at the thirdposition and to maintain said movable contact means engaged with thecontact connected with said common resistor terminal at the second andthird positions and engaged with the other of said spaced contacts atthe first position, so that in successive positions of said movablecontact means, said resistors are connected in series with said neutraland another supply conductor, one resistor is shunted across saidneutral and another conductor, and both resistors are shunted acrosssaid neutral and said other conductors.

5. In electrical apparatus for connection with a three-wire supplycircuit, a plurality of load devices, a selector switch means includingmovable contact means for successively energizing a plurality of spacedcontacts upon movement of operating means for said selector switch meansin one direction, electrical connections arranged to connect one or moreof said load devices in a plurality of different relations with respectto said supply circuit corresponding to difierent positions of saidoperating means including a pair of arcing switches each having a pairof separable contacts in certain of said connections, with certain ofsaid selector contacts connected, respectively, to one of said supplywires and to one terminal of said load devices, and with one contact ofone of said arcing switches connected to another of said supply wiresand another selector contact, and the other contact thereof connected toa terminal of said load devices, and to still another of said spacedcontacts, the other arcing switch having one contact thereof connectedto the third supply wire and its other contact connected to a thirdterminal of said load devices, and common operating means for saidmovable selector contact means and arcing switches for opening thecontacts of at least one of said arcing switches prior to deenergizationof a spaced contact, and for closing the contacts of at least one ofsaid arcing switches only after energize.- tion of the next succeedingspaced contact.

CHARLES H. HODGKINS.

